The speeds involved in a tap for a high pressure (above 200 bar) gas container are very high. For gases such as helium the speeds can be much greater than the speed of sound. With such speeds some plastic seats or inserts in the regulator valve cannot resist the adiabatic compression shock and can burn in the presence of an oxidizing gas. It is therefore useful to restrict the pressure and slow the speed of the gas to absorb the shock wave when opening the main valve of the tap for withdrawing gas.
In the prior art, filters were provided between the main valve and the regulator valve, but these filters have the disadvantage of slowing the gas flow when the container is nearly empty. In addition, filters can become clogged. As a result, they suffer shocks every time they are opened and can generate particles. At high pressure, which can be of the order of 300 bars or more, when the gas cylinder is full, known filters pose no problems and do not interfere with the flow. However, filters cause a constant pressure drop, and at low pressures, below 50 bars, pressure disturbances begin and become particularly detrimental at 10 bars. These known filters that cause a constant pressure drop therefore choke the gas expansion curve at low pressure.
Other, less damaging, solutions have been developed for when the container pressure decreases.
For example, Patent EP 1500854 A1 discloses a container tap provided with a non-sealing shutter located between an on/off valve and a regulator tap. The shutter is normally positioned across the flow area. When the valve is opened, the pressurized gas rapidly forces the shutter to a position across a restricted flow area so as to reduce the shock wave applied to the regulator valve. After the pressure equalizes across both sides of the shutter, the latter returns to its normal position across the full flow area.
U.S. Pat. No. 7,225,810 B2 discloses a container tap with a shutter similar to that in the previous document and operating in the same way.
These shutters certainly provide an interesting solution, however, they have the disadvantage of complexity linked to a reliability constraint, as well as a disadvantage in that they do not definitely prevent combustion when the valve is opened. Indeed, in the presence of impurities in the tap pathway and, especially in the presence of oxygen under high pressure, combustion can still occur and cause serious safety problems. Indeed, in the event of combustion, flames can escape from the tap and cause burns, damage to nearby equipment and/or cause fires.